Every day freight is shipped using various modes of shipping including trucks, trailers and aircraft. The freight is usually shipped inside storage areas and/or containers and some freight can be composed of flammable material. The freight often is stored in an area separate from personnel handling or watching over the truck, trailer, aircraft or storage facility. Consequently, the start of a fire in a container or storage area may go undetected for a prolonged period of time. Once a fire condition has been detected, the container or storage area in which the fire is located may not be immediately known because many different containers may be located in a storage area. Even when the fire is detected and the involved container located, access to the container may be difficult, as in the case where a number of containers are located in an aircraft cargo area in close-packed arrangement.
Freight carried by modern commercial freighter aircraft usually is transported in containers or on pallets. The containers or pallets are generally referred generically as Unit Load Devices or “ULDs”. The containers may be constructed of high-strength aircraft grade aluminum alloy, sometimes with sides constructed partially of Lexan polycarbonate. Under Federal Air Regulations, ULDs are considered aircraft appliances, are FAA certified for the specific type of aircraft, and are typically manufactured to specifications contained in National Aerospace Standard (NAS) 3610. An example of a very commonly used ULD for main deck freight stowage is an AMJ-type container configured to fit within the main deck stowage area. A number of these containers and/or pallets may be stored in a cargo area of the aircraft.
If a container contains flammable material and the temperature rises too high or the material is otherwise ignited, a fire could start in the container. Unless someone is in the cargo area at the time the freight combusts, which is unlikely, such a fire could remain undetected by the ground and/or flight crew. If undetected, the fire could spread to other containers or areas and compromise the aircraft.
U.S. Published Patent Application No. 2001/0054964 discloses a system for detecting and suppressing a fire condition in a storage unit. Sensors are provided to detect a fire condition and transmit detection of such an event to a control center, such as the cockpit of an aircraft. In addition, a fire suppression device is configured to discharge a fire suppressant material into the storage unit upon detection of the fire condition. In the case of a plurality of storage units, a plurality of sensors are employed along with a plurality of fire suppression devices for respective storage units.
The fire suppression devices disclosed in the above-mentioned published application include a source of pressurized fire suppressant material and a popup device disposed between one of the storage units and the source. The popup device is configured to apply the fire suppressant material to the storage unit upon detection of the fire condition. The storage unit may be a container with a base including a hole, and the popup device may include a valve aligned with the hole, such that the fire suppressant material is discharged into the container through the hole in the base. In an aircraft fire suppression system, the fire suppressant material may be centrally located and distributed via a manifold to the storage units.
Other fire suppression devices have used a liquid foaming agent and a pressurized gas for agitating and aerating the foaming agent to generate a foam. It has been proposed to provide an aircraft fire suppression system with respective supplies of a liquid foaming agent and pressurized gas that are connected to a plurality of fire suppression devices respectively associated with container and/or pallet locations in an upper deck freight storage area of an aircraft. The fire suppression devices each would be individually actuated upon detection of a fire condition in the associated container or pallet. A further proposal was to provide such a fire suppression device that could penetrate the container or pallet cover to deliver fire retardant foam directly to the contents of the container or pallet.